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Java Forum / General / December 2007servlet how to show "loading image"
I have a servlet that loads images, which are usually big. I want to show the message "loading image" when retrieving the image, and automatically shows the image once it is done. Any suggestions here? >I have a servlet that loads images, which are usually big. I want >to show the message "loading image" when retrieving the image, If you put a thin but obvious border around the space the image will occupy, images (at least JPGs and GIFs) are pretty efficient at showing their own 'load progress'. And they will demonstrate the progress with something much more interesting than an 'hourglass'. >..and automatically shows the image once it is done. Any suggestions >here? KISS.  SignatureAndrew Thompson http://www.physci.org/ > >I have a servlet that loads images, which are usually big. I want > >to show the message "loading image" when retrieving the image, [quoted text clipped - 14 lines] > > Message posted via JavaKB.comhttp://www.javakb.com/Uwe/Forums.aspx/java-general/200712/1 Andrew, I'm not quite sure I understand you clearly. What I want to show is dynamic loading image like http://www.ajaxload.info/ and automatically switches to the image once it has been loaded. ... >Andrew, I'm not quite sure I understand you clearly. I am also relatively confident that is the case. My take is that you are over-thinking this, and as a result, are about to make (yet) a(nother) crappy web. app. >What I want to show is dynamic loading image like http://www.ajaxload.info/ >and automatically switches to the image once it has been loaded. Ughh. Now that is pointless and stupid. Instead of an image that is scanning down the page line by line as it is loading*, I get to watch a sickening little 'twirly thing' that shows no indication of the % progress? One step forward, two steps back. * I am thinking JPEG there, as opposed to GIFs, which have a much smarter way to show 'some part' of the image early on. BTW - What format are the images? How big are the images (in px and bytes)? SignatureAndrew Thompson http://www.physci.org/ > .. > [quoted text clipped - 25 lines] > > Message posted via JavaKB.comhttp://www.javakb.com/Uwe/Forums.aspx/java-general/200712/1 The images are dynamically generated, in PNG format. Size varies. I'm thinking of going AJAX for that purpose. But not sure how to, any hint? ... >The images are dynamically generated, in PNG format. Smack 'em out to JPEG. That should reduce the size to at least a third. >..Size varies. How *much?* What is the frigging *minimum* and *maximum*? (Sheesh) Getting information from some people is like pulling teeth, from a chook. >I'm thinking of going AJAX for that purpose. But not sure how >to, any hint? Don't. SignatureAndrew Thompson http://www.physci.org/ > ... >> The images are dynamically generated, in PNG format. [quoted text clipped - 12 lines] > > Don't. There's a standard idiom for showing images in web apps - have a servlet serve'em up. Then Andrew's placeholder trick can work. <img src="/Imager?name=foo.jpg" /> I use this for, say, when images are stored in a database instead of a relative directory of the web app. Also useful for images created on the fly. SignatureLew >> ... >>> The images are dynamically generated, in PNG format. [quoted text clipped - 20 lines] > relative directory of the web app. Also useful for images created on > the fly. Or map Imager/* to your servlet so you can write <img src="Imager/foo.jpg"> if you want all browsers to understand that the image name is foo.jpg (should the user try to save the image). This specially applies to SonyEricsson mobiles if I remember correctly. //Roger Lindsjö > Or map Imager/* to your servlet so you can write <img > src="Imager/foo.jpg"> if you want all browsers to understand that the > image name is foo.jpg (should the user try to save the image). This > specially applies to SonyEricsson mobiles if I remember correctly. Nice tip. I can make immediate use of that - in fact, for a client's project. This newsgroup helps us earn a living. SignatureLew >> Or map Imager/* to your servlet so you can write <img >> src="Imager/foo.jpg"> if you want all browsers to understand that the [quoted text clipped - 5 lines] > > This newsgroup helps us earn a living. Glad to be of help, that's one of the main reasons I come here, almost every day I learn something new. //Roger Lindsjö > .. >> The images are dynamically generated, in PNG format. > > Smack 'em out to JPEG. That should reduce the size to > at least a third. IME that depends entirely on the image content. For images with continuously varying tone and high levels of detail, JPEG will give better compression (assuming you use lossy compression, as you know, you can set JPEG quality to 100% for effectively lossless compression). In other cases PNG can give better compression than JPEG. To achieve high compression with JPEG involves a tradeoff in quality which can lead to very noticable muddiness and ringing effects on images with flat-colour backgrounds. I'd try both. >> .. >>> The images are dynamically generated, in PNG format. [quoted text clipped - 3 lines] > >IME that depends entirely on the image content. True - good point. Technical drawings or blueprints can become blurry when the compression is high, and JPEG is pretty pointless when compression is low. But for these particular (line based) drawings, I would even recommend... >...For images with >continuously varying tone and high levels of detail, JPEG will give [quoted text clipped - 8 lines] > >I'd try both. .. trying dropping the colors to 256 and perhaps even rendering it as a (shock horror) GIF (or PNG*). Dropping the number of colors can result in a significant reduction in image byte size. > ..<http://www.libpng.org/pub/png/book/chapter01.html#png.ch01.div.2.3> * Huhh. That is neat. SignatureAndrew Thompson http://www.physci.org/ >>> What I want to show is dynamic loading image likehttp://www.ajaxload.info/ >>> and automatically switches to the image once it has been loaded. >> Ughh. Now that is pointless and stupid. Instead of >> an image that is scanning down the page line by line [quoted text clipped - 3 lines] >> What format are the images? >> How big are the images (in px and bytes)? > The images are dynamically generated, in PNG format. Size varies. > I'm thinking of going AJAX for that purpose. But not sure how > to, any hint? Have you tried generating *interlaced/progressive* PNG? http://www.libpng.org/pub/png/book/chapter01.html#png.ch01.div.2.3 Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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